827
FXUS66 KOTX 242228
AFDOTX

Area Forecast Discussion
National Weather Service Spokane WA
328 PM PDT Tue Sep 24 2024

.SYNOPSIS...

A ridge of high pressure will deliver above normal temperatures
through Wednesday. Strong winds accompany a cold front passage
Wednesday afternoon and evening. Areas of blowing dust along with
showers and thunderstorms will be possible with the frontal
passage. Temperatures return to near normal by Thursday with
another cold front passage Friday. Above average temperatures and
dry early next week.

&&

.DISCUSSION...

...ROBUST COLD FRONT TO BRING STRONG WINDS, BLOWING DUST, AND SHOWERS
AND THUNDERSTORMS....

Tonight and Wednesday: As the trough continues to press into the
Pacific Northwest, the ridge axis will shift east allowing for a
cold front to begin to press into the region. Overnight lows will
be unseasonably warm in the upper 50s and 60s. The start of
Wednesday will be quiet. Ensembles continue to show a major
pattern change during the day with a cold front passage starting
late morning and lasting into the late evening.

Wednesday will definitely be an interesting day. Ensembles
continue to bring the cold front through the Inland Northwest
1PM-8PM. The main impacts with the cold front will be strong
winds and isolated thunderstorms. With mostly clear skies before
the front, daytime highs will be similar to Tuesday reaching into
the 80s.

The rain and thunderstorm will start late morning over the
Cascades and spread East through the afternoon. Highest precip
amounts will be in the higher terrain of the Cascades, the
northern mountains, and Idaho Panhandle. These areas are seeing a
spread of 0.1-0.2" for 25-75% probabilities. The thunderstorm
threat is expected to be weak and isolated but has the potential
to occur any location in the Inland Northwest. The thunderstorms
could bring brief downpours and gusty outflows causing tree
damage and isolated power outages.

Winds will be main concern with frontal passage for the Basin and
valley locations. The winds will start to ramp in the late
morning, peak in the afternoon with passage, and dropping off
overnight. Ensembles continue to show sustained speeds into the
20-30 range with gusts up to 50 MPH for the Basin. The northern
valleys will see lighter speeds of 10-20 with gusts near 40 MPH.
Potential impacts from the winds will be choppy lakes, blowing
dusts, and fire concerns. For fire, the humidities will be on the
high side of critical but with the dryness of the fuels across the
Basin and winds, any new start has potential to spread rapidly.
The blowing dust concerns will be mainly across the Basin along
the I-90 and Hwy 2 corridors. But any location next to recently
worked fields can expect reduced visibility from blowing dust.
/JDC

Thursday through Friday: A low pressure system will track across the
Gulf of Alaska on Thursday and into western BC Thursday night. A
fairly robust warm front with a P-wat plume of over an inch will
push into southwestern BC and western WA by Thursday afternoon. The
trailing cold front will occlude with the warm front and push east
of the Cascades overnight Thursday into Friday morning. The parent
low will track well to the north of the Inland Northwest resulting
in a weakening frontal band. This will in turn result in decreasing
potential for precipitation across the Inland Northwest compared to
the west side of the state of Washington. There`s less than a 10%
chance for precipitation away from the Cascades with only increasing
cloud cover. Chances for precipitation increases to over 80% at the
Cascade crest with up to around a quarter of an inch of rainfall
expected. Very little cold air advection is expected with the
passage of the frontal occlusion overnight Thursday. This will
result in limited mixing and wind potential. Pre-frontal southerly
winds sustained of 10-15 mph with gusts of 20-25 mph is expected
around Grand Coulee, on the Waterville Plateau, and up the Okanogan
Valley. Westerly post-frontal winds will occur on Friday with
similar wind speeds across the exposed areas of the basin. This
frontal passage will bring winds around 10-15 mph weaker than what
is expected with the cold front passage tomorrow.

Friday night through Tuesday: The far extended part of the forecast
will remain active, but moisture may lacking as to produce
appreciable precipitation across the region. The next shortwave
disturbance to pass through will be on Sunday. This shortwave will
have much less moisture associated with it and also limited on
synoptic dynamics. It will bring passing high clouds but not much
else. Winds will be out of the north with gusts of up to around 20
mph down the Okanogan Valley, Waterville Plateau and over the
western basin. Shortwave ridging of high pressure moves in Monday
into Tuesday with temperatures above normal and highs warming into
the 70s. The next weather system to push through looks to be late
Tuesday. Preliminary outlook has this frontal system also weakening
as it traverses across the Inland Northwest with minimal to no
impacts anticipated. /SVH

&&

.AVIATION...
00Z TAFS: VFR conditions are expected through Wednesday morning.
Cirrus clouds will slowly filter through the region with stable
conditions over the region. A strong cold front will bring
westerly winds and chance for thunderstorms Wednesday afternoon
and early evening. Wind gusts in excess of 30 mph expected.
Localized areas of blowing dust could impact visibility across the
Basin impacting MWH-GEG-SFF-COE-PUW.

FORECAST CONFIDENCE AND/OR ALTERNATE SCENARIOS: High confidence
for VFR conditions at all TAF sites through tonight. Moderate
confidence on VFR through the period. Blowing dust is expected to
impact Basin sites during the afternoon and bring MVFR conditions.
Low confidence on the potential IFR conditions due to dust and
thunderstorms impacting TAF sites. /JDC

&&

.PRELIMINARY POINT TEMPS/POPS...
Spokane        60  85  46  70  50  73 /   0  20  40   0  10   0
Coeur d`Alene  58  84  48  69  49  72 /   0  10  60   0  10   0
Pullman        56  84  45  68  47  71 /   0  20  70   0   0   0
Lewiston       64  91  56  76  55  78 /   0  20  60   0   0   0
Colville       47  83  36  69  39  72 /   0  20  40   0  10   0
Sandpoint      53  80  45  65  45  69 /   0  20  70  10  10  10
Kellogg        62  82  50  66  51  68 /   0  10  80  10  10  10
Moses Lake     57  84  43  72  46  75 /   0  20  10   0   0   0
Wenatchee      62  80  48  71  54  72 /   0  40  10   0  20   0
Omak           58  84  43  71  48  74 /   0  30  10   0  20   0

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 11 AM to 11 PM PDT Wednesday for Central
     Panhandle Mountains-Coeur d`Alene Area-Idaho Palouse-
     Lewiston Area-Northern Panhandle.

WA...Wind Advisory from 11 AM to 11 PM PDT Wednesday for Lower
     Garfield and Asotin Counties-Northeast Blue Mountains-
     Northeast Mountains-Okanogan Highlands-Okanogan Valley-
     Wenatchee Area.

     Blowing Dust Advisory from 11 AM to 11 PM PDT Wednesday for
     Moses Lake Area-Spokane Area-Upper Columbia Basin-
     Washington Palouse-Waterville Plateau.

&&

$$